Reproductive Ecology Research Articles

Reproductive Dynamics of an Isolated Population of American Crocodiles (Crocodylus acutus) Based on Long-term Monitoring Data

The American Crocodile (Crocodylus acutus) is still considered Vulnerable, with some populations remaining depressed and showing little evidence of recovery. An understanding of the reproductive dynamics and parameters of C. acutus is essential for its conservation and management. Although the knowledge of C. acutus reproductive ecology has greatly increased during recent years, some critical parameters such as breeding effort (i.e., proportion of adult females that nest each year in a population) remain poorly known. Herein we analyzed 14 yr of reproductive data from a C. acutus population in a Mexican atoll to better understand its reproductive dynamics in space and time. We estimated the number of reproductive females in the population and in each nesting area, compared nest characteristics and clutch parameters among nesting areas, and determined female breeding effort and breeding frequency (i.e., proportion of years that an adult female nested). We estimated that 35 reproductive female C. acutus inhabit the main island of the atoll, distributed among 12 nesting areas. The annual female breeding effort ranged from 27.3–60.6% and the breeding frequency of 15 selected females ranged from 57.1–92.3%. Breeding effort depends on the breeding effort in preceding years. We also found significant differences in reproductive attributes (i.e., number of nests, nest–water distance, nest depth, clutch size, and nesting success) among nesting areas that we explain by the quality of those habitats for crocodile nesting and by territorial behavior of females.

Spawning Period and Size at Maturity of the Ocellate Spot Skate Okamejei kenojei in the West Sea of Korea

This study aimed to investigate the gonadal development process and size at maturity of the ocellate spot skate Okamejei kenojei (Müller and Henle, 1841). In total, 1234 specimens were collected from the center of the Korean West Sea between January 2019 and December 2020. The maturity stage of the gonads of each individual was determined visually based on size, color, and egg size. To estimate the spawning period, each specimen was measured for disc width, body weight, and gonad weight, and the monthly gonadosomatic index (GSI) was derived. The GSI of the specimens peaked in April and May, and the main spawning period occurred during June and July. Egg capsules were first observed in specimens collected in March and were most commonly observed in specimens collected in July (56.8%). The maturity ogives for disc widths of female specimens at 50%, 75%, and 97.5% maturity were 26.6, 27.9, and 30.8 cm, respectively, whereas those of male specimens were 26.2, 27.5, and 30.7 cm. The findings of this study provide basic information on reproductive ecology related to the fertility of the ocellate spot skate.

“Reproductive Ecology of Narrow mouthed frog Microhyla ornata”

: Reproductive ecology of Narrow mouthed frog Microhyla ornata was studied at selected breeding sites around Dharwad, Karnataka India during the wet periods between May 2017 and December 2018. The breeding activity varied depending upon the amount of rainfall. It was higher during monsoon when there was higher rainfall, whereas, when rainfall was scanty less activity was observed. Males begin the calling activity in the evening after the sunset at 1098min reaching its peak at around 1200min and extend till the early morning of the next day. Gravid females arrive at the breeding site one to one and half hour after the calling was initiated in the early pre-monsoon and monsoon period and amplexus took place soon after the arrival of females within one hour during peak calling days. Size assorted matting was observed in M. ornata and showed significant positive correlation. The female body size was positive correlation with clutch size. However, there was no significant correlation between female body size and egg size. Breeding activity of M. ornata spanning for seven months suggest that, this species is a prolonged breeder. The eggs and larvae of M. ornata were under constant threat by the predatory larva of the aquatic insects like Dragonfly and Water beetle. Few clutches during non rainy period faced the risk of desiccation. The breeding sites of many anurans are affected by urbanization and habitat fragmentation. There is a need to adopt the strategy to conserve the habitats to protect the species.

Influence of researcher experience and fieldwork intensity on the probability of brood losses in sensitive species: The case of the Red-backed Shrike Lanius collurio

Minimizing disturbance to animals when studying them should be a major consideration in ecological research design, especially when species are known to be sensitive to disturbances. A basic method in the study of bird reproductive ecology involves nest visits, but these can adversely affect birds’ breeding success. Appropriate fieldwork procedures are therefore highly important, especially in the case of timid and sensitive species. This study aimed to assess the impact of the method of searching for nests of Red-backed Shrike Lanius collurio on the probability of these birds abandoning their broods. Our study revealed that observer experience and nest searching intensity did influence the likelihood of brood desertion by this species. Less field experience and a greater nest searching intensity caused the shrikes to abandon their nests more often. We recommend paying scrupulous attention to the behaviour of the birds when searching for nests and when looking for nests after incubation has started.

Trends in plant ecology research in Ethiopia (1969-2019): Systematic analysis

Background: The current status of plant ecology research in Ethiopia is unknown with the result that it is challenging to judge the impact of existing research on policy development and conservation actions.Objectives: The objective of this paper was to systematically analyse the trends in plant ecological research in Ethiopia over the past 50 years.Methods: The inclusion and exclusion of articles for analysis was carried out using the Reporting Standards for Systematic Evidence Syntheses (ROSES) flow diagram developed for systematic review/meta-analysis.Results: The number of articles published, authors and collaboration has increased dramatically since the 1960s. Most of the research (52.6%) focused on the Dry evergreen Afromontane Forest and grassland complex (DAF) and Moist evergreen Afromontane Forest (MAF) vegetation types. Of the remaining vegetation types, woodlands (14.3%) i.e. Acacia–Commiphora woodland and bushland proper (ACW), and Combretum–Terminalia woodland and wooded grassland (CTW), desert and semi-desert scrubland (DSS) (2.3%), and the Afroalpine (AA) and Ericaceous Belt (EB) (1.5%) received comparatively little attention. Classical plant ecology themes and descriptive plant community studies were dominant over the last five decades in contrast to the focus on contemporary themes globally. Reproductive and dispersal ecology of invasive plant species and pollination ecology seem to be largely neglected topics. Furthermore, the recommendations forwarded by most of the articles reviewed (38.1%, n = 51) were not result-based. Conclusions: As a future direction, the Ethiopian government should develop a project database for both completed and ongoing projects.

Reproductive Traits of the Vent Crab Segonzacia mesatlantica (Guinot, 1989) From the Mid-Atlantic Ridge

Characteristics of the life-history biology of hydrothermal vent species are a prerequisite to understanding the dispersal, population connectivity, and ecology of these insular populations. The vent crab Segonzacia mesatlantica (Guinot, 1989; Brachyuran: Bythograeidae) is one of the most dominant endemic predators at deep-sea hydrothermal vents along the Mid-Atlantic Ridge (MAR). However, the biological life-history characteristics remain poorly understood for this species. The objective of this study was to reveal relevant biological characteristics of the reproductive ecology of S. mesatlantica, contributing to a better understanding of its ecology and the importance of the maintenance of healthy populations. The reproductive ecology of S. mesatlantica from the Broken Spur vent field such as the in situ behavior of brooding female crabs, gametogenesis, fecundity, and the embryonic and larvae development was studied. In contrast to non-brooding crabs, brooding crabs of S. mesatlantica were observed at the vent periphery exhibiting a sequence of specific brooding behaviors, suggesting that they might be providing oxygen to their embryo mass. Results from histological analysis reveal the presence of oocytes in different stages of development within the gonad. Once extruded, the mature oocytes form an egg mass underneath the abdomen. Similar to other bythograeid crabs, the egg mass of S. mesatlantica was composed of a high number of relatively small eggs in different stages of embryonic development. The eggs hatch as a first zoea that undergoes at least four stages of development.

Evolutionary interactions between thermal ecology and sexual selection

Thermal ecology and mate competition are both pervasive features of ecological adaptation. A surge of recent work has uncovered the diversity of ways in which temperature affects mating interactions and sexual selection. However, the potential for thermal biology and reproductive ecology to evolve together as organisms adapt to their thermal environment has been underappreciated. Here, we develop a series of hypotheses regarding (1) not only how thermal ecology affects mating system dynamics, but also how mating dynamics can generate selection on thermal traits; and (2) how the thermal consequences of mate competition favour the reciprocal co-adaptation of thermal biology and sexual traits. We discuss our hypotheses in the context of both pre-copulatory and post-copulatory processes. We also call for future work integrating experimental and phylogenetic comparative approaches to understand evolutionary feedbacks between thermal ecology and sexual selection. Overall, studying reciprocal feedbacks between thermal ecology and sexual selection may be necessary to understand how organisms have adapted to the environments of the past and could persist in the environments of the future.

Soft coral reproductive phenology along a depth gradient: Can "going deeper" provide a viable refuge?

Many species across a wide range of taxa and habitats display phenological shifts and differences in response to both environmental gradients and climate change. Moreover, the wide‐scale decline of numerous ecosystems is leading to increasing efforts to identify zones that might serve as natural refuges from various disturbances, including ocean warming. One such refuge was suggested to be that of the deep coral reefs, but whether depth can provide coral populations with a viable and reproductive refuge remains unclear. Given the global coral‐reef degradation and the key role that corals play as ecosystem engineers, their reproductive ecology has been widely studied. A particular knowledge gap nonetheless exists regarding coral reproductive phenology along a depth gradient. Filling in this gap may uncover the environmental cues that regulate coral reproduction, leading to better predictions of population connectivity, and their possible responses to climate change and other environmental changes. Here, using long‐term in situ observations of the soft coral Rhytisma fulvum's reproductive activity along its entire depth range (0–45 m), we examined the relationship among several environmental factors and the coral's reproductive phenology and activity over five successive annual breeding seasons. Compared with the shallow depths, a lower number of reproducing colonies was found in habitats deeper than 30 m, highlighting possible constraints on coral reproduction at the deeper end of their range. Our results further revealed that an increase in seawater temperature over 1–2‐day intervals during the breeding season correlated with the onset of reproductive activity along the depth gradient, leading to different reproductive periodicities in different depths. These differences suggest that differential temperature regimes and reproductive timing across depth may create intraspecific temporal reproductive segregation, possibly reducing connectivity among populations along a depth gradient. Moreover, we found high variability among years in both the timing of breeding activities and in the level of reproductive synchrony among corals from different depths. Overall, our study questions whether depth can provide a long‐term and viable refuge for corals in the face of global environmental changes.

Influence of physical environmental parameters on the abundance of Chrysichthys nigrodigitatus of the Cross River, Nigeria.

In this study, the influence of physical environmental factors (rainfall, temperature, water depth, turbidity, transparency and conductivity) on the temporal distribution, abundance and catch of C. nigrodigitatus from the Cross River was investigated. Fish catch and abundance were monitored fortnightly for 12 months. Surface water samples were collected twice monthly and analyzed using standard methods. Seasonal variations in rainfall, water depth, temperature, turbidity, transparency and conductivity were observed across the study period. Correlation analysis showed a positive and significant relationship between rainfall and fish catch (P<0.05), while temperature and conductivity were negatively correlated with fish catch (P<0.05 and 0.01 respectively). Transparency was negatively correlated with fish catch but this relationship was, however, not statistically significant (P>0.05). On the other hand, water depth and turbidity were positively correlated with fish catch but again both relationships were not statistically significant (P>0.05). These findings suggest that rainfall, temperature, conductivity and other environmental variables play important role(s) in the distribution and abundance of Chrysichthys nigrodigitatus in the Cross River, with implication of climate change impact on the species reproductive ecology and population dynamics.

Results of quantitative count of not numerous species of pacific salmon at the fish enumeration facility in the headwaters of the Ozernaya River (Western Kamchatka)

Results of investigations of spawning run and quantitative assessment of Pacific salmon (pink salmon, chum salmon, coho salmon and chinook salmon) obtained during counting the sockeye salmon at fish enumeration facility in the headwaters of the Ozernaya River. It is revealed that abundance of various Pacific salmon species except sockeye salmon reaches significant values in some years in Kurile Lake. The presented data supplement knowledge about biology and reproductive ecology of pink salmon, chum salmon, coho salmon and chinook salmon.

Subterranean Life-Style Does Not Limit Long Distance Dispersal in African Mole-Rats

Dispersal from the natal site to breeding sites is a crucial phase in the life history of animals and can have profound effects on the reproductive ecology and the structure of animal societies. However, few studies have assessed dispersal dynamics in subterranean mammals and it is unknown whether dispersal distances are constrained by living underground. Here we show, in social, subterranean Damaraland mole-rats (Fukomys damarensis), that a subterranean lifestyle does not preclude long distance dispersal and that both sexes are capable of successfully dispersing long distances (&amp;gt;4 km). Body condition did not predict dispersal distance, but dispersers from larger groups traveled farther than individuals from smaller groups. Subsequently we show in a phylogenetically controlled comparative analysis of dispersal distances in subterranean and surface-dwelling rodents that living underground does not constrain dispersal distances and that dispersal capacity is mainly a consequence of body size in both lifestyles.

Spawning schedule of the imperiled Bigeye Chub (Hybopsis amblops) in Illinois

The Bigeye Chub (Hybopsis amblops) once inhabited streams and rivers in eastern and southeastern Illinois and was thought to be extirpated in the state by the 1970s. However, it was rediscovered in the 1990s from the Little Vermilion River. Today, H. amblops has become widespread and locally abundant in streams of the Wabash River drainage. Currently, little is known about the spawning and reproductive ecology of H. amblops. We conducted a study in the Salt Fork Vermilion River to determine the spawning schedule and microhabitats of H. amblops. Based upon near-weekly samples in May and June in 2019 and 2021, we determined H. amblops spawns in moderate water velocity over sandy gravel substrates when water temperatures are between 18–22 °C. Understanding such ecological traits is necessary for the continued success of H. amblops throughout its range.

Use of a wireless ultrasound probe as a portable, noninvasive method for studying reproductive biology in the asp viper, Vipera aspis.

In this study, we investigated the use of wireless ultrasonography as an imaging system to study the reproductive ecology of the asp viper (Vipera aspis), a viviparous snake found in southwestern Europe. Female vipers were captured during the summer and immediately scanned to obtain an estimate of the number of embryos. Ultrasound imaging was performed with a pocket‐sized wireless ultrasound probe interfaced with a tablet with a dedicated app. Vipers were then released at the exact capture site after collecting data on body size and weight. We validate wireless ultrasonography as a non‐destructive, effective tool for ultrasonic investigations in the field. Wireless probes are light and compact, which facilitates carriage in rugged terrain. Moreover, the absence of cables simplifies the maneuvers to be made on a small, potentially dangerous snake. Importantly, ultrasound scans can be performed at the capture site, thus minimizing restraint time and handling of gravid females.

Compensating for Small Body Size: The Reproductive Ecology of Southern Spotted Turtle (Clemmys guttata) Populations

Gradients in environmental conditions across a species' geographic distribution can drive variability in a variety of life history traits. In North American freshwater turtles, both body and clutch size have commonly been shown to vary latitudinally, and these two traits are often directly related, with larger individuals producing larger clutches. We studied the reproductive ecology in two Georgia populations of Spotted Turtles (Clemmys guttata) from 2016–2020 by attaching radio transmitters to female turtles during the breeding season. We x-rayed turtles to determine clutch sizes and used thread bobbins to locate nesting locations, allowing us to determine nest fates. Across all Spotted Turtle clutches (n = 41), mean clutch size was 2.1 (range: 1–4) eggs per clutch. Approximately 92% of individuals that we monitored produced at least one clutch during the breeding season, and we identified 16 instances of individuals producing more than one clutch in a single year, including six turtles triple clutching during 2018. We located 24 Spotted Turtle nests during the study, nine (37.5%) of which either hatched or partially hatched. The other nests were either depredated (41.7%), did not hatch due to infertility or environmental reasons (8.3%), or had an undetermined fate (12.5%). Our results indicate that annual reproductive output in southern Spotted Turtle populations can exceed that of northern populations where individuals produce a single larger clutch per reproductive season. Finally, opportunistic observations in Florida from 2014–2021 indicated that the reproductive season can begin over a month earlier than in southern Georgia, highlighting the variability in reproductive ecology even across a relatively short latitudinal distance.

Population density, feeding and, reproductive ecology of rodents from Alemsaga Priority State Forest and adjacent farmlands

A study on population density, feeding, and reproductive ecology of rodents from Alemsaga Priority State Forest and the adjacent farmlands was conducted from July 2018-September 2020. Live and snap traps were used for capturing rodents from the study area. The Capture-Mark-Release method was employed to estimate the population size and respective density of rodents. Snap traps were used to capture rodents for body measurement and stomach content analysis. Embryo count was carried out from 64 pregnant females. Data were computed using descriptive statistics and compared with chi-square. Lophuromys simensis, Arvicanthis abyssinicus, Desmomys harringtoni, Mastomys natalensis, Stenocephalemys albipes, Rattus rattus, Arvicanthis dembeensis, Mus musculus, and Acomys cahrinus were recorded from the six habitats. The result indicated that a total of 1140 and 171 individuals were trapped in the study area with live and snap traps, respectively. The average population density of rodents was 47.4 h-1. The highest density was recorded in bushland habitat (75.1 h-l) while the least was in Carissa land (32.2h-l). In terms of species, L. simensis showed the highest density (111.65 h-l) whereas A. cahrinus was the lowest (1.7 ha-1). The overall densities of rodents were 224.82 ha-1 and 162.93 ha-1 during the wet and dry seasons, respectively. The total rodent biomass in the study area was 160,495 g. The number of embryos counted ranged from 4-12 and 2-8 during the wet and dry seasons, respectively. However, there was no statistical significance between the two seasons (χ2 = 0.74, df=1, p&gt; 0.05). Plant matters constituted a higher proportion of stomach contents (64.4%) compared to animal matters (13.2%). Generally, Alemsaga State Forest harbors rodent species with high density and biomass. Proper conservation of the area will contribute to the betterment of species density and biomass.

Pollination ecology and breeding system of Ecbolium Ligustrinum (Acanthaceae): a transition from autogamy to xenogamy through specialised plant-pollinator interactions

In view of the ongoing rarity ofEcbolium ligustrinumthere is an urgent need for conservation of the species. For this, a detailed work was carried out regarding the untold story of its reproductive ecology. The work was done for three consecutive years (2015–2017) at Midnapore, West Bengal over three different populations collected from three different areas of West Bengal. Field data were also recorded from these three wild populations. The species produces gullet flowers with bi-labiate corolla having long slender tubes. The flowers exhibit one day of longevity. The flowers are visited by 10 species of insects. Among those, four species viz.Eristalis tenax, a Dipteran member and three ant species of Hymenoptera such asCamponotussp.,Formicasp. andMonomoriumsp. are the effective pollinators. As per pollination efficiency,Eristalis tenax(PEi= 0.76) is the most successful one. The flowers are shortly protandrous (dichogamous) and passed by three distinct reproductive (male, bisexual and female) phases. The breeding system clearly depicts that the species is facultatively xenogamous supported by myophilous mode of pollination. However, geitonogamous type of pollination is also observed through myrmecophily, an atypical instance found in plants. Lastly, the plant retained some sort of autogamy through ‘fail-safe’ mechanism of pollination, an adaptation which might be developed in absence of pollinators. Therefore, undoubtedly it can be concluded thatE. ligustrinumis a partially self-incompatible (ISI = 0.27) species having a mixed mating system, adapted for xenogamy through specialised mode of plant-pollinator interactions.

A 24-year investigation of the reproductive ecology of the Edible Dormouse (Glis glis)

The Edible Dormouse is a non-native rodent introduced to the Chilterns, UK, in 1902. It shows extreme annual variation in breeding; either having one litter per year or, in some years, failing to breed at all. Despite this slow reproductive rate compared to other rodents, its population is increasing, and has spread beyond the anticipated landscape barriers. Communal nesting is sometimes observed. This study aims to characterise the reproduction parameters over time, including from communal breeding. Based on a population of &amp;gt;11,000 PIT-tagged individuals, 600 litters and 4000 nestlings at our Chilterns study site over 24 years, we show the best fit of the number of new-borns is an increasing exponential. Monthly weight of nestlings also increased over the 24 years, while annual reproduction rate, litter size and nestling growth rates remained unchanged. Litter size decreased from 6.6 new-borns in August to 4.3 in October, indicating an average death rate of 37% in the first two months of life. Preliminary analysis suggests a small decrease in death rate over the years. Average growth rate of nestlings was c.100% of birth weight per week in their first month, but then slowed. We also examined evidence of kinship between nest sharers and investigated whether this, or communal breeding in general, promotes offspring survival. Our results will provide a deeper insight into the factors that drive the reproductive success of this invasive species and enable investigation of the effect of climatic variables on the number, survival and growth rate of nestlings.

Floral biology, floral volatile organic compounds and floral visitors of Chromolaena odorata, an invasive alien species in West Bengal, India

Abstract. Layek U, Das A, Das U. 2022. Floral biology, floral volatile organic compounds and floral visitors of Chromolaena odorata, an invasive alien species in West Bengal, India. Biodiversitas 23: 2118-2129. Chromolaena odorata (L.) R.M. King &amp; H. Rob. is a fast-growing weed native to the Neotropics and introduced in several regions of Africa, the Pacific Islands, and Southeast Asia, including West Bengal in India. It is one of the world’s most widespread and troublesome invasive alien plant species (IAPS) that severely infest natural habitats and crop fields. However, extensive data documents about the reproductive ecology are unknown, especially within West Bengal. This study assesses the floral biology, floral volatile organic compounds (VOCs), and floral visitors of the weed. The weed species flowers from October to January. Florets are white to purple, with short, narrow corolla tubes and deep-seated nectar. Abundant VOCs are benzyl stearate, 2,4-decadienal, n-hexadecanoic acid, 1-hexyl-2-nitrocyclohexane, and o-decyl hydroxylamine. Flower heads were visited by numerous insect groups, though the diversity of Lepidoptera (mainly butterflies) was higher than the other insect orders. The weed is pollinated by diverse insect groups (e.g., butterflies, flies, honeybees, leafcutter bees, solitary bees, and wasps). However, vital pollination services to the weed were provided by butterflies (based on the ‘approximate pollination value’). Our findings may conclude that the clustered capitula, longer stigmatic receptivity, and broad array of pollinators resulted in too much fruit set. It is one of the critical factors that support the high growth rate and invasive nature of the weed in dry habitats.

Reproductive Ecology of Drosophila obscura: A Cold Adapted Species.

The study of insect reproductive ecology is essential to determine species distributions and fate under changing environments. Species adapted to harsh environments are good examples to investigate the reproductive mechanisms that allow them to cope with the challenging conditions. We here focus on studying for the first time the reproductive ecology of a cold-adapted Drosophila obscura (Diptera: Drosophilidae) strain collected in Finland (subarctic climate region). We tested several reproductive traits such as fertility and fecundity to observe the onset of reproduction and gauge when sexual maturity is reached in both males and females. We combined these measures with an analysis of changes of their reproductive organs shortly after eclosion. We found that males matured several days before females and that this process was underpinned by female egg maturation and male accessory gland growth, while sperm was already present in two-day old males. This delayed maturation is not observed to the same extent in other closely related species and might be a signature of exposure to harsh environments. Whether this delay is an adaptation to cope with variation in resource availability or prolonged unfavorable temperatures is though not clear. Finally, our study adds to the set of reproductive mechanisms used by cold adapted species and the information presented here contributes to understanding the breadth of Drosophila reproductive ecology.

Factors Affecting Seed Germination of the Invasive Species Symphyotrichum lanceolatum and Their Implication for Invasion Success.

Invasive species Symphyotrichum lanceolatum (Willd.) G. L. Nesom is spreading uncontrollably along wet habitats as well as in disturbed ecosystems. All those habitats function as corridors that facilitate seed dispersal. One way to prevent the spread of invasive species is to know their reproductive ecology. The present study evaluates the potential for generative reproduction of S. lanceolatum and determines how different temperatures, amounts of nutrients, and light regimes, affect seed germination. Seeds collected from 13 natural populations were germinated at four fluctuating temperature regimes (15/6, 20/10, 30/15, and 35/20 °C). To test the influence of nitrate on seed germination, two KNO3 concentrations were used (5 mM and 50 mM solution). For each treatment, three replicates of 30 seeds were placed in complete darkness or a 14 h photoperiod. The results showed that the germination increased with increasing temperature. The optimal temperature regimes were 30/15 °C and 35/20 °C with approximately 88% germination. The overall effect of KNO3 on germination was positive. The concentration of 50 mM KNO3 had a less stimulating effect compared to 5 mM KNO3. Seeds showed sensitivity to lack of light during germination but were able to germinate in a significant percentage in such conditions. Considering that S. lanceolatum often occurs in disturbed sites, these results suggest that seed reaction to alternating temperature, nutrients concentration, and light can be determining factors that affect seed germination of this species and, thus, its spread.